AN EFFICIENT SOLUTION PROCEDURE FOR THE ONE-STEP EXPERIMENT

The ONE-STEP experiment(1) describes an experimental procedure for det ermining the hydraulic properties of a soil sample. It involves measur ements of cumulative out flow with time from a soil core placed in a p ressure cell. The water flow in this soil core satisfies the classical Richards equation. The accuracy of numerical schemes for simulating t his experiment strongly depends on experimental conditions. In case th e pneumatic head applied to the pressure cell is high the solution is characterized by a ''steep drying front.'' A small spatial discretizat ion step size is then required to obtain accurate solutions. To improv e the efficiency of the procedure for determining soil hydraulic prope rties, we have studied the applicability of a simple variable step siz e scheme.